I have spent the past few days in the Rocky Mountains where the temperatures ranged from -27 to -35 degrees not factoring in windchill. Here is my experience of using a Nikon D200 and Nikkor 18-200 for a couple of days at this temperature. At the bottom is an itemised list of what happens to the hardware at these temperatures, so skip to that if you don't want the full fun story:

Day1:
Well out trip through Alberta takes us from Lake Louise to Jasper through the national parks on what is the coldest temperature I have ever experienced. The camera went through two cold spots, the first of which at Lake Louise where at 8pm the temperature was -27 degrees not factoring windchill. I wanted to do a long exposure of the lake 2min walk from the hotel, so a shirt, longsleeved shirt, jumper, jacket, and skijacket later I was on my way.

The camera mounted on a borrowed Velbourn carbon fibre tripod (thankgod, because a metal one would have been even colder to carry around), was setup at the lake as per normal with a time of 12 minutes. I pushed the button and started running around to keep warm. Less than 20 min later the JobNr process failed with a low battery. I tried heating the battery at the fireplace but no luck, it was dead dead.

When I got back to the hotel an hour later, condensation formed on the tripod and outershell of the camera which instantly froze into a frost. Very cool but made me very worried. Also I got to my hotel room and figured that the purplish colour of my toes and dark red and very painful fingers were a sign that simple socks and shoes, and gloves were insufficient for this kind of weather. Warm water for 20 min fixed them. But oh did they ache.

Day2:
Day 2 was more intense. In Jasper there was -35 degrees at 10am about the time when we went hiking up the Columbia Ice Fields which were at a higher altitude and somewhat windy. Just a few interesting notes about this temperature. I was wearing:
- 2 socks, thermal underwear, jeans, and ski pants,
- shirt, longsleeved shirt, jumper, jacket, and ski jacket,
- cotton gloves, ski gloves, scarf, face mask, ski goggles, beanie and a hood.
This made me barely comfortable. At these temperatures your breath freezes instantly on your goggles, your eyes water from the cold, and this water causes your eyelashes to freeze together when you blink. Also if you breath out through your nostrils and then in again, your nose hairs freeze which feels like 100 tiny pinpricks in the nose. I don't think I was too far off from having my spit go clunk as it hits the ground too. Anyway, on to the trip:

On the way up the ice fields I noticed, as I did at Lake Louise, that my camera LCD started to slow down. Forget 15ms refresh rate, it was more like 300ms. A little time later the LCD started getting so slow that when showing the blown highlights in the preview it no longer flashed black and white, but just smoothly switched between shades of gray. The buttons on my camera also became intermittent, combined with the LCD at the top of the camera becoming faint and slow it made shooting in manual almost impossible so I switched back to A priority, underexposed and hoped for the best. At this point about 1 hour into the trip I had taken close to 100 photos and my first battery was nearly dead. I kept it in my pocket when not shooting learning from the mistake at Lake Louise. (My jean pocket since it was warmer not my ski pants pocket). I noticed a few noises too. Mainly my shutter or rather the mirror sounded much louder and slower than normal. Instead of the soft click it made a loud clonk. Also autofocus was making a straining wheezing sound.

2nd hour into the trip and it is starting to get somewhat difficult to breath (I normally live in a +35 degree coastline, not a -35degree 3500m high mountain). Autofocus started to fail. When focusing at details on the mountains every 3rd or 4th time it would fail to reach the infinity point. The focus wouldn't hunt, so I knew the camera was trying, but just jammed before the infinity and then blink the focus failed indicator. I blame the Nikkor 18-200mm itself because it is crap, and it also became very hard to zoom past about 135mm (normal for this lens, but not this hard!). At this point my battery died, and disaster, my goggles froze over which lead to mild but still painful snowblindness later that day.

3rd hour in and my radio broke so at this point I turned around very pissed not to have reached the top of the glacier, and I was not going to go any further alone (I really shouldn't have been up there in winter in the first place). Anyway a few more photos I turned and started a panorama, and after 2 photos I was greeted with what sounded like part of a shutter release and that was it. I tried turning the camera off and on and ended up with ERR in the viewfinder, and sort of fading in and out (trying to blink) on the top LCD. After a few whacks on the body I got it going again with an audible clunk only to have it fail a few photos further on. Time to try something else.
I put the camera into my under jacket and sat down for about 15 minutes while enjoying the view. I managed to get the radio going again the same way but it was still time to turn around (my eyes were starting to hurt). I pulled the camera out of my jacket and it nearly instantly turned white. Condensation had formed and suddenly frosted over the entire camera, and the front lens element was now covered with ice. Wiping it off got no where, so I eventually got the ice off the middle of the front element by licking the lens and wiping very quickly. I got just enough ice off the camera to get a usable picture out of it, finished my panorama, and hurried back down the glacier.

Back down the glacier the car was already running thanks to me radioing ahead, and the camera went straight onto the heater which avoided much of the condensation issue (although in retrospect could possibly stress some of the components). Everything was back in order, and because it was the day before Australia day we were greeted with the incredible surprise of the local liquor store in Jasper; stocking Australian beer, and not just the crap VB, good Tasmanian beer! A James Boags premium, a hot-tub, and the comfort of my travel insurance made me forgive all what my camera had just been through.

So there you go. Extreme cold, it worked, but only just

Itemised List:

Camera itself: No permanent damage. During use I could hear the Rapid Return Mirror getting audibly slower. It started sounding more like someone hitting a metal drum than a quick snap. After 3 hours it suffered total failure. The reflex mirror jammed mid exposure. Turning the camera off and on resulted in "ERR" being displayed where the aperture normally goes. Hitting the camera and turning it off and on again released it, however it rejammed 5 shots later. The mirror returned to normal once the temperatures did.

Autofocus (18-200mm): After 2 hours the autofocus became notably slower and louder. I would assume that the gearing is to blame here. Several times it failed to reach the infinity focusing point despite clear contrast and bright conditions. The camera was trying to move the AF because otherwise it would focus hunt before displaying the AF fail indicator.

Zoom ring (18-200): Not much to say given that this lens is crap to begin with, but in the cold it became even harder to use this zoom lens. I blame the non-IF design of the lens.

Battery life: This is the biggest problem. At -35 a full battery managed to take 1 12minute exposure but did not finish the Noise reduction. The camera lasted less than 20 min of continuous exposure. When shooting normally a full battery was down to 70% capacity after only 15 normal shots. Normally I get over 80 shots before the 70% mark is reached. Warming the batteries does not return them to life, only recharging them does. Keep batteries in your pocket until it is time to take the photo. With this method I managed to take just over 100 photos over a 2 hour period before the battery died.

LCD displays: LCDs become very slow to react. This goes for the main LCD and the settings LCD on the top of the camera too. When using the flashing blown highlights indicator (flashes white and black) it eventually only smoothly changed between shades of grey. It took more than a full second to fully update any LCD. The viewfinder LCD was less affected however it did become noticeably faint.

Camera buttons: Several electrical contacts became intermittent. The thumbwheel and index wheel especially so. It came to a point where shooting in manual was impossible as it was too hard to change the shutter speed more than 1 or 2 stops.

Condensation: At these temperatures if you get condensation on your lens it is over. It will instantly freeze and once it does it is almost impossible to get off the lens without heating the equipment up first.

Good report! Another thing to note that if you bring your camera and lenses inside from those temps (especially seeing condensation start building up), you should have them sealed in an airtight bag prior to any condensation forming. Bring them up to room temp slowly. All that condensation you seen on the outside of the lens and body, can also happen inside the lens and bodies. Now you have moisture ruining electronics and possibly mold/fungus growing in lenses. I carry large gallon zip-lock bags. Put gear in bags, suck out the air and seal. I do this both entering the cold and returning to the warmth.

In my humble opinion, the problem with the auto focus and the zoom was caused by the lubricant used. This is a very common problem with any mechanical object in extreme cold. You would have had the same problem with any lens, auto or manual. Batteries are renowned for losing their charges in real cold. plus the fact that the mechanicals put more power drain on the battery.
As far as condensation is concerned, I have found in dealing with rifle scopes, that it is best to leave them in the cold dry air. Warm air is moist and the moisture will deposit on the warm surface. I seem to remember that cold weather equipment, larger batteries, camera warmers, and the such are available for those who are facing this kind of cold more than occasionally. A mechanical film camera is a good idea as a back up, provided your film does not shatter.
JS

I wouldn't put too much faith in all mechanical cameras. My winters aren't anywhere near as bad as described above, but cold weather has killed 3 of my favorite mechanical film cameras. For crazy cold temps you need specially designed gear.

well Hey, I mean when are you usually in lower than below -30 degree weather out to take pictures? There are more extreme colds, but if you get much colder you might want to have a new camera waiting for you when you get back